Disclaimer: I wrote the library that I am sharing here.
My somewhat new library mphx may be able to help you. It can manage 'rooms' of connections, allows client to server and server to client messaging in the form of events, and best of all, is cross platform. It also works in the web with websockets.
It was originally an extention of HxNet, however I wanted it to be easier to use. Connecting and sending a 'message' with data just takes a few lines.
I have a few examples in the github repository, the simplest being the 'basic' example. One of your requests you have is that it doesn't rely on one of the big libraries (open fl, etc) and mphx doesn't. The basic example proves that, and only runs in terminal. That being said, it can be used with haxeflixel, for that you can see the other examples.
It sounds like your main goal is to have simple, graphic multiplayer. For that you can look at the 'movement' haxeflixel example.
Documentation is still a little skim, and the code is alpha, so it might change or break. That can probably be said for most of the library's you listed though. The best way to install it is like this
haxelib git mphx https://github.com/5Mixer/mphx.git
That will not install the examples though. To run them, either download the repository as a zip, or just git clone
it, and go into the examples folder.
Library: https://github.com/5Mixer/mphx
Old video's I made. A little outdated, most likely.
Video 1: https://www.youtube.com/watch?v=07J0wLXwH0g
Video 2: https://www.youtube.com/watch?v=MUx2CUtsnTU